My experience with a Dos 10m and now RPM 10m 2009:
With the Dos 10m I found that as soon as there was NO tension even on just one steering line, it wanted to drop towards the water fast. Even when walking down the beach making up ground I had to keep lots of tension on the lower steering line. Obvious to see in a way that the bar is not parrallel to the front tube. In comparison: the RPM 10m I have now, does not do that. The bar can stay parralel to the front tube. Same thing on the water.The RPM 10m keeps floating as long as there is only very little bit of wind because of riders speed. With the Dos 10m even with lots of wind it drops towards the water fast when having no tension on one or both steering lines.
So I think a lot of kites will do better then a Dos 10m.